Small Footprint MII/RMII 10/100 Ethernet Transceiver for Automotive Applications
Datasheet
3.2
Auto-Negotiation
The purpose of the auto-negotiation function is to automatically configure the transceiver to the
optimum link parameters based on the capabilities of its link partner. Auto-negotiation is a mechanism
for exchanging configuration information between two link-partners and automatically selecting the
highest performance mode of operation supported by both sides. Auto-negotiation is fully defined in
clause 28 of the IEEE 802.3 specification.
Once auto-negotiation has completed, information about the resolved link can be passed back to the
controller via the Serial Management Interface (SMI). The results of the negotiation process are
reflected in the Speed Indication bits of the PHY Special Control/Status Register, as well as in the Auto
Negotiation Link Partner Ability Register. The auto-negotiation protocol is a purely physical layer
activity and proceeds independently of the MAC controller.
The advertised capabilities of the transceiver are stored in the Auto Negotiation Advertisement
Register. The default advertised by the transceiver is determined by user-defined on-chip signal
options.
The following blocks are activated during an auto-negotiation session:
Auto-negotiation (digital)
100M ADC (analog)
100M PLL (analog)
100M equalizer/BLW/clock recovery (DSP)
10M SQUELCH (analog)
10M PLL (analog)
10M Transmitter (analog)
When enabled, auto-negotiation is started by the occurrence of one of the following events:
Hardware reset
Software reset
Power-down reset
Link status down
Setting the Restart Auto-Negotiate bit of the Basic Control Register
On detection of one of these events, the transceiver begins auto-negotiation by transmitting bursts of
Fast Link Pulses (FLP), which are bursts of link pulses from the 10M transmitter. They are shaped as
Normal Link Pulses and can pass uncorrupted down CAT-3 or CAT-5 cable. A Fast Link Pulse Burst
consists of up to 33 pulses. The 17 odd-numbered pulses, which are always present, frame the FLP
burst. The 16 even-numbered pulses, which may be present or absent, contain the data word being
transmitted. Presence of a data pulse represents a “1”, while absence represents a “0”.
The data transmitted by an FLP burst is known as a “Link Code Word.” These are defined fully in IEEE
802.3 clause 28. In summary, the transceiver advertises 802.3 compliance in its selector field (the first
5 bits of the Link Code Word). It advertises its technology ability according to the bits set in the Auto
Negotiation Advertisement Register.
There are 4 possible matches of the technology abilities. In the order of priority these are:
100M Full Duplex (Highest Priority)
100M Half Duplex
10M Full Duplex
10M Half Duplex (Lowest Priority)
Revision 1.1 (05-26-10)
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SMSC LAN88710AM/LAN88710BM
DATASHEET
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